Example of setting default parameter values in JavaScript

First type:

function test (a,b) {

var a = Arguments[0]? Arguments[0]: 1;//The default value of setting parameter A is 1

var B = arguments[1]? ARGUMENTS[1]: 9;//The default value of setting parameter B is 9

return a+b;

It is equivalent to

function Test () {

var a = Arguments[0]? Arguments[0]: 1;//The default value of setting parameter A is 1

var B = arguments[1]? ARGUMENTS[1]: 9;//The default value of setting parameter B is 9

return a+b;

}

Call Example

Alert (test ()); Output 10

Alert (Test (5)); Output 14

Alert (Test (5,6)); Output 11

Alert (Test (null,6)); Output 7

Alert (Test (6,null)); Output 15

The second type:

function test (blog,address) {

blog=blog| | ' Forgotten ~ shallow thinking ';

address=address| | ' Www.jb51.net ';

Alert (' Blog name is ' +blog+ ' address is ' +address ');

}

It is equivalent to

function test (blog,address) {

if (!blog) {blog= ' forgotten ~ shallow thinking ';}

if (!address) {address= ' www.jb51.net ';}

Alert (' Blog name is ' +blog+ ' address is ' +address ');

}

Call Example

Test (); The name of the blog is forgotten ~ The address of the shallow thinking is www.jb51.net

Test (' csdn ', ' blog.csdn.net '); The blog name is Csdn's address is blog.csdn.net

Test (', ' blog.csdn.net/u011043843 '); Blog name is forgotten ~ Shallow thinking

The third type:

function test (setting) {

var defaultsetting={

Name: ' Program Enthusiast ',

Age: ' 1 ',

Phone: ' 15602277510 ',

QQ: ' 259280570 ',

Message: ' Welcome to your join '

};

$.extend (defaultsetting,setting);

var msg= ' name: ' +defaultsetting.name

+ ', Age: ' +defaultsetting.age

+ ', Tel: ' +defaultsetting.phone

+ ', QQ Group: ' +defaultsetting.qq

+ ', Description: ' +defaultsetting.message

+ '. ';

Alert (msg);

}

Call Example

Test (); Output: Name: Program enthusiasts, Age: 1, Tel: 15602277510,qq Group: 259280570, Description: welcome you to join.

Test ({

Name: ' Dwqs ',

Age: ' 20 ',

QQ: ' 461147874 ',

Message: ' Blog: www.jb51.net '

});

Output: Dwqs, Age: 20, Tel: 15602277510,qq Group: 461147874, Description: Blog: www.jb51.net.

PS: The function parameters are relatively long, you can use this method. This is an extension of jquery, so you need to introduce jquery.